Purpose Retinal changes are poorly described in early treated phenylketonuria (ETPKU).
We aimed to investigate possible visual functional and ocular microstructural changes
in adult patients with ETPKU. Optical coherence tomography (OCT) and its angiography
(OCTA) data from patients with PKU were compared to healthy controls. Methods In this
prospective, monocentric, cross-sectional, case-control study 50 patients with ETPKU
and 50 healthy subjects were evaluated with OCT and OCTA. Measurements were performed
on right eyes. The following visual function parameters were studied: best corrected
visual acuity (BCVA), spherical equivalent (SE), contrast sensitivity and near stereoacuity;
microstructural parameters: retinal nerve fiber layer thickness (RNFLT), ganglion
cell layer (GCC) thickness, focal loss of volume (FLV), global loss of volume (GLV),
peripapillary, papillary vessel density (VD), ocular axial length (AL) and intraocular
pressure (IOP). Results Among functional tests there were significant differences
in contrast sensitivity at 1.5 (p < 0.001), 6 (p < 0.013), 12 (p < 0.001), 18 (p <
0.003) cycles per degree, in near stereoacuity (Titmus Wirt circles, p < 0.001) and
in best corrected visual acuity (BCVA, p < 0.001). A statistically significant, moderate
positive linear correlation was observed between BCVA and average Phe levels over
the last ten years (β = 0.49, p < 0.001). The average (p < 0.001), superior (p < 0.001)
inferior GCC (p < 0.001), the FLV (p < 0.003), GLV (p < 0.001) and the average RNFLT
(p < 0.004) values of the PKU group were significantly lower than the controls. The
serum phenylalanine level (Phe) in the PKU group negatively correlated with inferior
(−0.32, p < 0.007), superior (r = −0.26, p < 0.028) and average (−0.29 p < 0.014)
RNFL and with AL (−0.32, p < 0.026). In AL we detected a significant difference (p
< 0.04) between the good and suboptimal dietary controlled group. There was no significant
difference between the ETPKU and control group in the measured vessel density parameters
and in IOP. Conclusions Our results suggest that functional and ocular microstructural
defects are present in patients with PKU, and some of them may depend on dietary control.
The mechanism is unclear, but the correlation indicates the importance of strict dietary
control in terms of preservation of retinal functions.
